A large-eddy simulation on a deep-stalled aerofoil with a wavy leading edge
A large-eddy simulation on a deep-stalled aerofoil with a wavy leading edge
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DOI：
10.1017/jfm.2016.841
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发表时间：
2017-01
影响因子：
3.7
通讯作者：
Rafael Perez-Torro;J. Kim
中科院分区：
文献类型：
--
作者：
Rafael Perez-Torro;J. Kim
本文对NACA0021型正弦波前缘翼型在基于弦雷诺数$Re_{\infty }=1.2\times 10^{5}$和迎角$\unicode[STIX]{x1D6FC}=20^{\circ }$条件下的失速流动特性进行了数值研究。观察到层流分离泡（LSBs）在水波槽区以一种搭配的方式形成，而不是均匀/周期性地分布在跨度上。研究发现，lsdb的分布及其对气动力的影响很大程度上取决于模拟的展向域大小，即所使用的WLE的波数。本文还详细讨论了从WLE产生的一对反旋转的流向涡及其作为lsdb和相邻完全分离的剪切层之间的界面/缓冲的演变。目前的模拟结果证实，与之前的实验结果一样，与直前缘（SLE）相比，采用WLEs可以提高升力，降低阻力。此外，在周期性涡脱落频率下，WLE情况下气动力的非定常波动水平显著降低。在目前的模拟中观察到的三个主要事件归因于以下有利的空气动力学特性：(i)在LSBs产生的前缘附近出现了一个大的低压区；（ii）尾流板后面的流动重新附着，导致后尾迹的体积减小；（iii）由于展向相干结构的破坏导致von-Kármán（周期性）涡脱落的恶化。
A numerical investigation on the stalled flow characteristics of a NACA0021 aerofoil with a sinusoidal wavy leading edge (WLE) at chord-based Reynolds number $Re_{\infty }=1.2\times 10^{5}$ and angle of attack $\unicode[STIX]{x1D6FC}=20^{\circ }$ is presented in this paper. It is observed that laminar separation bubbles (LSBs) form at the trough areas of the WLE in a collocated fashion rather than uniformly/periodically distributed over the span. It is found that the distribution of LSBs and their influence on the aerodynamic forces is strongly dependent on the spanwise domain size of the simulation, i.e. the wavenumber of the WLE used. The creation of a pair of counter-rotating streamwise vortices from the WLE and their evolution as an interface/buffer between the LSBs and the adjacent fully separated shear layers are discussed in detail. The current simulation results confirm that an increased lift and a decreased drag are achieved by using the WLEs compared to the straight leading edge (SLE) case, as observed in previous experiments. Additionally, the WLE cases exhibit a significantly reduced level of unsteady fluctuations in aerodynamic forces at the frequency of periodic vortex shedding. The beneficial aerodynamic characteristics of the WLE cases are attributed to the following three major events observed in the current simulations: (i) the appearance of a large low-pressure zone near the leading edge created by the LSBs; (ii) the reattachment of flow behind the LSBs resulting in a decreased volume of the rear wake; and, (iii) the deterioration of von-Kármán (periodic) vortex shedding due to the breakdown of spanwise coherent structures.